The linksys WRT54G is a good router, have had mine for several years now and no problems, even had new firmware released for it a few times.
It has NAT functionality and a basic firewall built in and Linksys are owned by Cisco so you know the build quality is good.
http://www.linksys.co.uk/acatalog/Wi...e_Routers.html
you can buy them here :-
http://www.lambda-tek.com/components...how=&Filter=GO